Backpackers are being sexually harassed, underpaid and exploited by unscrupulous employers in regional Australia, the workplace watchdog has found.

And most of them won't complain, fearing a backlash from their employers.

A two-year national inquiry into the conditions of working holiday visa holders has confirmed recent reports some are being taken advantage of.

The Fair Work Ombudsman report released today found not only was it common for workers to be underpaid, some were not paid their wages at all.

Sexual harassment, withholding passports without permission, and payment for tools and equipment that the business was meant to provide were also common.

Some workers were asked to pay for their jobs and accommodation, while others worked for free in exchange for non-certified accommodation.

More than a third surveyed in the report said they were paid less than the minimum wage, while 14 percent said they had to pay before getting work and six percent had to pay an employer to 'sign off' on their regional work requirement.